a. Field of the Invention
The present invention relates to pencils not requiring sharpening, and more particularly to such pencils which comprise a core material and a thermoplastic resin sheet which has been uniaxially stretched. The resin sheet is wrapped around the core material so that a stretched direction of the sheet forms a spiral against the core material, whereby the sheet is formed as a holder for the pencil.
B. Description of the Prior Art
Conventional pencils not requiring sharpening are fabricated by wrapping paper around a lead material (i.e., a mixture of graphite and clay). In these conventional pencils, the paper is perforated for stripping off and the lead material can be exposed by a length corresponding to a distance between adjacent perforations by stripping off paper along a perforation.
Such conventional pencils have a defect of poor waterproofness because the holder material is paper, and in addition, there is a problem that a length of the exposed lead material is limited to a width between adjacent perforations of the paper holder material. The width of paper between perforations cannot be made as narrow as desired when the strength of paper, treating, ease of manufacture, etc. are taken into account. Further it takes much labor to make such narrow or closely spaced perforations. Furthermore, in the case of the conventional products, surface covering treatment was indispensable to hide the perforations after wrapping around the lead material so as to improve the appearance of the outer surface. This surface covering makes stripping off of the surface difficult and it becomes necessary to insert a thread under the surface covering.